Public clouds now offer computing services with a variety of pricing schemes. Spot servers, which offer large cost savings, are an increasingly popular platform on which applications are being deployed. Spot servers are dynamically priced and require users to submit a bid. In this article, the authors show the effect of bidding on application cost and availability when running on spot servers. Based on their analysis, they present simple and effective bidding strategies for users and provide motivation for new research directions in cloud resource management and fault tolerance.